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i.MX8QM Surround View System - Pixel Format Issue

Question asked by Wayne Kuo on Sep 15, 2019
Latest reply on Sep 16, 2019 by Rita Wang

Hi Experts,

 

I'm setting up NXP's Surround View System demo with i.MX8QM MEK.

Software is Linux L4.14.98_2.0.0, but replace OpenCV version to OpenCV 3.4.

 

I'm facing an issue of input / output data format.
I checked OV10635 datasheet, the default Camera output format is 8-bit YUYV.
However, App Demo code use 32bits RGBA as V4L2 input.

 

It makes me confuse, the camera output format should be the same with V4L2 input format?

 

I also done some check:
1. I used "v4l2-ctl -d /dev/video0 --list-formats-ext | grep Format" command to get the available pixel format form camera and got the following list, I also used these formats to be the V4L2 input pixel format and got the result:
1) RGBP: See attachment "RGBP.jpg"
2) RGB3: See attachment "RGB3.jpg"
3) BGR3: Segmentation fault
4) YUYV: Segmentation fault
5) YUV4: See attachment "YUV4.jpg"
6) NV12: Segmentation fault
7) YM24: Segmentation fault
8) XR24: See attachment "XR24.jpg"
9) AR24: See attachment "AR24.jpg"
Seems only using 32-bits format as V4L2 input format can get the whole frame, but the color format is not correct.

 

2. I used the "takeFrame" function in demo code to get the single frame and use OpenCV "imwrite" to save picture. I found the demo code use OpenCV "cvtColor" to do a RGBA-to-RGB transform. But as I told, I think the camera output is 8-bits YUYV format. If there is a YUYV format save in a 8UC4 OpenCV Mat, RGBA-to-RGB transform should cut the V channel, so the saved image's color is not correct.

 

3. Base on the input format is YUVY theory, I tried to use OpenCV to do a YUYV-to-RGB transform. However, OpenCV YUYV-to-RGB transform only accept 8UC2 format as input (It means only 16-bits format accepted). But for the 1. test, the input should be 32-bits format.

 

My question is:
1. What is the correct V4L2 input format for the Surround View System demo?
2. If the input format is 8-bits YUYV, how can I done the YUYV-to-RGB transform by OpenCV?
3. If I want to use ISI to do the YUYV-to-RGB transform, is there any simple way to do this?
4. Anything wrong for my understanding?

 

Thanks.

 

BR,
Wayne

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